French justice officials have opened legal proceedings against seven of 12 alleged jihadists arrested in sweeps across France on Oct. 6, during which one suspect died in a shootout with police. Though insufficient evidence of terrorist plotting led to five of those individuals being freed on Oct. 11, officials said raids conducted the previous day — which uncovered guns, bombmaking materials and proof of intent to carry out strikes — allowed the other seven suspects to be placed indefinitely under detention as members of a “terrorism cell” determined to “commit attacks on national territory.”

French authorities also revealed other evidence in the case corroborating TIME’s Aug. 31 exclusive report on the growing allure of the conflict in Syria among French Muslim extremists seeking jihadist experience. Some of the seven suspects remanded in custody intended to travel to Syria to fight alongside Islamist militants battling the regime of President Bashar Assad, according to authorities. Two were also described as having worked to recruit and facilitate travel of French extremists to Syria.

Those developments on Thursday came a day after French authorities announced they had unearthed weapons in a Paris suburb and an array of materials that Paris prosecutor François Molins described as “useful in the making of what are known as improvised explosives.” The chemicals, pressure cookers, cables, alarm clocks and other components were reminiscent of homemade bombs used in the wave of attacks in France in 1995–96 that killed 13 and injured 281 — the last successful terrorist campaign in France using explosives.

“In terms of dangerousness and extent of preparations, we’ve not seen any like this since 1996,” Molins said on Thursday in announcing the case against the seven suspects for “association with criminals involved in a terrorist enterprise.” He said a second legal dossier for “association with criminals seeking to join jihadist groups” had also been lodged against suspects who’d been planning to join combatants in Syria, or who’d helped others to do so.

Molins said the seven suspects are 19 to 25 years of age, all French-born citizens and all recent converts to Islam — most during prison terms for delinquent crime. Four had written wills, according to Molins, and one was carrying a loaded gun when apprehended. Two had made extended visits to Egypt and Tunisia of late.

The group is considered responsible for the Sept. 19 grenade attack on a kosher grocery store north of Paris that injured one person and whose “intent was to kill,” Molins said. It’s yet to be established if the two individuals who executed that strike are among the seven in custody. But DNA traces from the suspect killed in the Oct. 6 police raid — and considered the leader of the cell — was found on the grenade used in that attack. Sweeps targeting other group members also turned up lists of Jewish establishments, possibly as future targets. Heightened police protection of Jewish facilities was ordered in the wake of those discoveries — especially with France’s Jewish community still traumatized after being targeted in this past March’s murder spree of self-declared al-Qaeda radical Mohammed Merah.

Though debate still rages on about possible intelligence failure in the Merah case, Molins stressed on Thursday that preventive police action this time allowed “a terrorist attack on our country to be averted.” Perhaps just as importantly, that activity may also remedy legal difficulties of charging the suspects accused of seeking to assist the jihad in Syria — and facilitate future prosecution of French extremists with similar ambitions.

As TIME reported in August, French counterterrorism authorities had previously established that one group of aspiring French jihadists recently crossed from Turkey into Syria to take up arms with Islamists battling the Assad regime. Less definitive intelligence information that officials still consider solid indicates additional French radicals have similarly joined jihadist forces in Syria.

That, French security officials tell TIME, suggests the nation’s budding extremists are increasingly seeking to gain training, combat experience and terrorist instruction in nearby Syria rather than striking out for traditional militant hotspots like Pakistan, Afghanistan, Iraq or Yemen. “And if that’s happening among French radicals, I can’t imagine they’re alone among their European peers to be making such moves,” says a French counterterrorism official.

And for good reason: French and other European recruits can access Syria via Turkey — a popular tourist destination — usually without having to obtain visas that increase the risk of detection by intelligence services back home. The potential of Syria growing stronger as a magnet for such Islamists, French officials note, grows each week as endless fighting grinds on, and scenes of willful slaughter and civilian massacre by Assad forces proliferate across TV screens and online — serving as the kind of motivational propaganda for neophyte Islamists that al-Qaeda has relied on for years.

Also vexing is the legal void in which French antiterrorism officials say they find themselves regarding nationals who travel to fight in Syria — or those facilitating that transit. “In Syria, you don’t have Islamists shooting American or NATO troops, so charging fighters returning to France as enemy combatants doesn’t stick,” one ranking French security official says. “So far, attacks by radicals in Syria haven’t clearly crossed the line between ruthless strikes against the regime and terrorism per se. Legally speaking, then, we can’t file charges against someone going to fight a bloody regime whose ouster most Westerners support — no matter how notorious or dangerous their allies are in that effort.”

The network busted in the Oct. 6 raids may help solve that dilemma. Justice officials will now likely seek to establish a link between manifest domestic terrorist intent by the apprehended cell and the objectives of its members to link up with the Syrian jihad. If they’re successful in that, authorities may use it in the future as a legal precedent demonstrating activity on behalf of an extremist cause abroad that inevitably fuels action advancing that same cause at home — and vice versa. It seemed that logic was at work on Thursday when French Justice Minister Christiane Taubira told Europe 1 radio that everything stemming from the Oct. 6 sweeps shows “we aren’t underestimating either the internal, or external threat” of cells like the one now behind bars.